Thanks for the link. Has this been online for a long time already? It's the first time I've heard about it.

It's the first time anyone heard about it. There have been all sorts of rumours and ambiguous statements regarding the next album for a very long time now but no one knew when it was coming or what it would be called.

They did the same thing with In Rainbows, when no one found out about it until they made the announcement 10 days before release. But this time they even one-upped themselves by decreasing that window from 10 days to 5.

The reason they've been doing that is because their previous album (Hail to the Thief) leaked online long before it release date so they wanted to prevent leaks. What better way than to not even announce an album's existence until immediately before release?